1. Field of Invention
The present invention relates to amine modified polysaccharides and more particularly it relates to solutions and gels of amino acid-modified pectins formed by enzyme-catalyzed reactions.
2. Description of the Prior Art
Pectin is a highly branched complex polysaccharide that is commonly used in food formulations. Structurally, it consists of D-galacturonic acid residues linked together through .alpha.-1,4-glycosidic bonds and interrupted by rhamnose residues. Additional sugar branches are substituted at the rhamnose. The extent and distribution of substitution depend upon the source of the pectin and on the method of isolation. The polygalacturonic acid is partly methoxylated at the C-6 positions and free acid groups may be partly or fully neutralized with sodium, potassium, or ammonium ions The pectin obtained by the manufacturing process is high ester pectin.
It is known that many factors such as molecular weight, the non-uronide content, and methoxy content may influence gelation properties of pectin. It is also known that one of the most important properties of acidic polysaccharides is the ability to interact with positively charged counterions. Thus, sodium, potassium, calcium and magnesium have significant effect on the gelation of pectin. A large amount of calcium ions can render pectin completely insoluble (R. L. Whistler, J. N. BeMiller, Industrial Gums, 3rd Ed., Academic Press, New York, 1991).
Pectins can interact with lysine (Mahoney, R. R.; Farrell, C; Wetherby, A. M., Food Chem. 1982, 9: 289-294) as well as the basic polypeptides, namely, poly(L-lysine) and poly(L-lysine-alanine-alanine) (Bystricky, S.; Malovikova, A.; Sticzay, T, Carbohydrate Polymers, 1990, 13: 283-294). It has also been reported that pectin interacts with polylysine to form polyelectrolyte complexes (Japanese Patent: JP 9213741 A2 and JP 0413741). However, the complex formed is not stable and does not cause significant change in the properties of pectin in terms of viscosity and gelling ability.
Gelation and viscosity are highly desirable properties; however, commercial pectin, as is, usually shows relatively low viscosities.